A bath treatment is carried out by stopping the
flow of water to a tank and adding the chemical. After a
predetermined amount of time, the water flow is restarted.In tanks and ponds with a large volume, the level of the pond
will be lowered to approximately half and the pond then treated. The
water flow will then be turned on and the pond allowed to fill up
and then run as normal. This reduces the amount of chemical used.
Bath treatments are also used in cages, where a tarpaulin is pulled
around the cage to enclose it and the chemical added. At the end of
the treatment period the tarpaulin is removed.

Flush

A slug of chemical is added to a raceway or trough
and allowed to pass down through the raceway with clean freshwater
following behind. This is used in applications where it is
impossible to turn the water off for a bath treatment due to
limitations such as a lack of oxygen. This is used to good effect
with eggs but with fish, their ability to swim through the chemical
into the clean water, above gives variable results as the contact
time cannot be guaranteed.

Drip

A constant supply of chemical at a low
concentration (usually from a dosing pump, but sometimes form a
simple device like a bucket with a hole in it) intotank over a long period. Drips are sometimes with the
antifungal chemicals used for eggs. Care must always be taken not to
overdose the animals/ova, especially if the chemical used si one
which can build up in the bloodstream (such as the copper in copper
sulphate)

Dip

A quick (usually lasting less than one minute)
treatment where fish are immersed in a chemical solution (usually of
a high concentration). The easiest method for this is to net the
fish from the tank and immerse the whole net and fish into the
chemical. Used primarily for immersion vaccination, but also for the
treatment of some parasites.

Swab

A piece of cloth or cotton wool is dipped into a
high concentration of chemical and wiped of the fish. Impractical
for large numbers of fish but sometimes used for the treatment of
localised infections on valuable broodfish.

Injection

Injection of chemicals into the body of the fish is
a process used by many farms for the administration of vaccines.
Vaccines fall into one of four categories : 1. Intramuscular -where
the chemical is injected into the muscle of the fish, improved
results are gained if it is injected into the red muscle as the
greater blood supply to this area ensures quick distribution round
the body, 2.Intraperitonal - where the chemical is injected into the
body cavity. 3. Intravenous - Injected into the bloodstream, which
is largely impractical in most fish as locating the site is
difficult, 4. Subcutaneous - Injected beneath the skin but not into
the muscle. Both methods 1 and 2 give the best results with methods
3 and 4 not as effective. Injection of chemicals makes them act much
faster than other types of administration and so are often used for
valuable fish such as broodstock.

Oral

Mixing of chemicals such as antibiotics with the
feed is an effective method of treating large numbers of fish. The
feed is usually sprayed or coated with oil before mixing the
chemicals in as this makes them stick to the pellets and prevents
them being washed off as soon as the pellet hits the water. As appetite
is often reduced as a result of infections, there can be
difficulties in getting the fish to eat the medicated feed if
treatment is left too late. This is particularly so with some
antibiotics such as sulphonimides which impart an unpleasant flavour
to the fish and so reduce the appetite even more.